select dummy_id, date_registered, item_id, quantity, price,
(select sum(quantity)
from t t2
where t2.item_id = t.item_id and
t2.date_registered <= t.date_registered
) as cumulative
from table t;
Output:
ID
Date
Item
Qty
Price
Cumm
1
14-05-2014
1201
5
100
100
2
18-05-2014
2012
1.05
300
400
3
25-05-2014
2013
5.8
50
450
4
31-05-2014
2014
20
400
850
